Radio transmitter and radio receiver with channel condition assessment

ABSTRACT

FM radio transmitter is being widely used in portable devices as a convenient way to output audio contents to ubiquitously available FM radio receivers in cars or homes. However, the signal from the FM radio transmitter may be interfering with the signal being broadcast by an FM radio station. A scan system is incorporated into the FM radio transmitter to quickly and reliably identify a vacant channel for the FM radio transmitter to use. The scan system measures on-channel and out-of-channel signal quality and selects a best channel for transmission based on the measured on-channel and out-of-channel signal quality. The scan system is also incorporated into an FM radio receiver to quickly and reliably tune to a valid channel. The scan system selects the valid channel based on the measured on-channel and out-of-channel signal quality.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a division of U.S. Non-Provisional patentapplication Ser. No. 12/473,281, filed on May 28, 2009, entitled “RadioTransmitter and Radio Receiver with Channel Condition Assessment”, whichclaims priority to U.S. Non-Provisional patent application Ser. No.12/137,535, filed on Jun. 11, 2008, entitled “Frequency Modulation (FM)Clear Channel Scanning System and Method of Using Same.” The U.S.Non-Provisional patent applications are hereby incorporated by referencein their entireties

FIELD OF THE INVENTION

The present invention generally relates to radio transmitters and radioreceivers and particularly to a FM radio system and method of using sameincorporating channel condition assessment.

DESCRIPTION OF THE PRIOR ART

FM (Frequency Modulation) radio transmitter has been widely used inportable devices such as cellphone, MP3 (MPEG-1 Audio Layer 3) player,PDA (Portable Digital Assistant), and PMP (Portable Media Player) tooutput audio contents on the device to an external FM audio receiver.The FM radio provides an instant wireless audio link between theportable device and the FM audio receiver that is available almosteverywhere worldwide. This wireless link allows a user to playback theaudio contents onto the FM radio receiver in a car for safer driving.Also a user may enjoy the better audio quality usually available in acar or home radio receiver. The FM radio transmitter may comply with theworldwide FM audio broadcast standard (for example, the FM broadcastsystem in US occupying a nominal spectrum from 87.5 to 108 MHz or anyother similar FM systems). The radio transmitter may also be an AM(Amplitude Modulation) system that complies with the worldwide AM audiobroadcast system (for example, the AM broadcast system in US occupyingthe nominal spectrum from 520 to 1710 kHz or other similar AM systems.

On the other hand, FM radio receiver is even more widely used inportable devices such as cellphone, MP3, PDA, and PMP. The FM radioreceiver provides a user the convenience to enjoy FM radio listeningexperience anywhere anytime. Paired with a portable device equipped withan FM transmitter, the portable devices may share audio contents amongthem. In another application, the FM receiver may be used as a wirelessearphone to be paired with a portable device equipped with an FMtransmitter.

In the radio transmitter application, scanning for and finding anunoccupied or vacant channel for transmission and avoiding interferencewith licensed broadcast or other undesirable channels is highlydesirable in an effort to increase efficiency and quality and to takeadvantage of such available channels. If the selected channel fortransmission is also being used by a local broadcast radio station, thetransmission from the portable device will interfere with the signalbeing transmitted from the local radio station. This will result in poorreception quality of the signal from the portable device, or otherwisethe portable device may have to transmit at a much higher power level to“over-power” the local radio station which may interfere with theintended reception of the local radio and may violate the regulatorycompliance. Consequently, it is extremely important to scan for anunoccupied channel before the portable device starts to transmit.

As an example, currently, in the United States, the frequency modulation(FM) broadcast band falls generally within 87.5 to 108.0 megahertz(MHz). Existing FM scanning systems use spectrum analysis to identifyvacant (or available) channels. In doing so, a received signal strengthindicator (RSSI) is used. The RSSI is a measurement of the power presentin a received radio signal. The RSSI typically consists of a one-byteinteger value. A value of 1 indicates the minimum signal strengthdetectable, while a value of 0 indicates no detectable signal. Currentscanning systems identify vacant channels based solely on the RSSImeasurement. If the RSSI is higher than a specified threshold, then thecandidate channel is identified as occupied, and if the RSSI is lowerthan a specified threshold, the candidate channel is identified asvacant. This strategy fails to take into account of the noise leakage ofneighboring occupied channels. Open (or available) channels surroundedby neighboring channels with high RSSI strengths require greaterreceiver performance for clear reception. However, open channels withouthigh RSSI strength neighbors are received clearly by receivers withlesser performance capability.

Existing scanning systems fail to accurately identify open channels withlow RSSI strength neighbors. Existing scanning systems search for openchannels by making a single pass through the entire range. This methodof scanning is time consuming, and suffers from poor accuracy.

Existing scanning systems also fail to utilize past scan results whenidentifying open and occupied channels. Because different channels mayhave different strengths at different distances, each scan of the rangemay return with different results. Therefore, the reliability of thescanning results suffers because the results of past scans gounutilized. Therefore, it is desirable to identify an open channel thatis free from potential interference from strong neighboring channels toensure high quality transmission at the identified open channel.

In the radio receiver applications, automatically tuning to a channelhaving a good signal quality is a convenient feature. This isparticularly important for portable devices where the usage of thedevices is often in a mobile environment such as walking, jogging, anddriving. Again, existing FM radio receivers often use automaticallytuning systems based on spectrum analysis to identify strong-signalchannels. In doing so, a received signal strength indicator (RSSI) isoften used. This strategy may identify a channel with signals spilt fromstrong neighboring channels. The identified channel may result in pooraudio quality due to the interference from neighboring channels havingstrong signal strength. Therefore, a reliable automatic tuning orautomatic seek is very desirable for radio receivers in portabledevices. Furthermore, the scan system should also assess the possibleinterference of the identified channel and provide estimated parametersto the receiver to alleviate the potential interference.

In light of the foregoing, the need arises for a scanning system withimproved accuracy, speed, and reliability of identifying a vacantchannel in the radio transmitter application. On the other hand, thereis a need for a reliable automatic tuning or automatic seek for radioreceivers in portable devices to quick and reliably tune to a channelwith good signal quality.

BRIEF SUMMARY OF THE INVENTION

The present invention provides radio transmitter systems and radioreceiver systems incorporating a scan system to select a channel fortransmitting or receiving respectively.

In one embodiment, a radio transmitter incorporates a scan system toselect a channel for transmission, wherein the transmitter accepts anaudio input signal and uses transmit path circuits to provide atransmission signal, and the scan system receives signals from a receiveantenna and measures on-channel signal quality and out-of-channel signalquality of the received signal so as to select the channel for the radiotransmitter.

In another embodiment, a radio transmitter incorporates a scan systemusing two or more sub-bands to select a channel for transmission,wherein the transmitter accepts an audio input signal and uses transmitpath circuits to provide a transmission signal, and the scan systemreceives signals from a receive antenna and measures on-channel signalquality and out-of-channel signal quality of the received signal so asto select the channel across all sub-bands for the radio transmitter.

In yet another embodiment, a radio transmitter incorporates a scansystem to select a channel for transmission, wherein the transmitteraccepts an audio input signal and uses transmit path circuits to providea transmission signal, and the scan system receives signals from areceive antenna and measures on-channel signal quality andout-of-channel signal quality of the received signal so as to select thechannel for the radio transmitter, wherein parts of the scan system maybe implemented in the radio transmitter system.

In an alternative embodiment, a radio transmitter incorporates a scansystem to select a channel for transmission, wherein the radiotransmitter and the scan system share an antenna.

In one embodiment, a radio receiver incorporates a scan system to selecta channel for receiving, wherein the receiver accepts a signal from areceive antenna and uses receive path circuits to generate an outputaudio, and the scan system receives signals from the receive antenna andmeasures on-channel signal quality and out-of-channel signal quality ofthe received signal. The scan system generates the channel for the radioreceiver to tune based on the on-channel signal quality. Furthermore,the scan system provides the out-of-channel signal quality to the radioreceiver so that the radio receiver can apply digital signal processingmatched to the out-of-channel signal quality to optimize audio quality.

In another embodiment, a radio receiver incorporates a scan system toselect a channel for receiving, wherein the receiver accepts a signalfrom a receive antenna and uses receive path circuits to generate anoutput audio, and the scan system receives signals from the receiveantenna and measures on-channel signal quality and out-of-channel signalquality of the received signal so as to generate the channel for theradio receiver to tune, wherein the scan system is implemented in theradio receiver.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following detailed description ofthe preferred embodiments which make reference to several figures of thedrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of FM clear channel scan system.

FIG. 2 shows a block diagram of a radio transmitter system incorporatingtransmit path circuits and a scan system.

FIG. 3 shows a block diagram of a radio transmitter system incorporatingtransmit path circuits and a scan system where parts of the scan systemare implemented in the radio transmit circuits.

FIG. 4 shows a block diagram of a radio receiver system incorporatingreceive path circuits and a scan system.

FIG. 5 shows a block diagram of a radio receiver system incorporatingreceive path circuits and a scan system where parts of the scan systemare implemented in the radio receive circuits.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providea more thorough explanation of embodiments of the present invention. Itwill be apparent, however, to one skilled in the art, that embodimentsof the present invention may be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form, rather than in detail, in order to avoidobscuring embodiments of the present invention.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment can be included in at least one embodiment of theinvention. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments mutuallyexclusive of other embodiments. Further, the order of blocks in processflowcharts or diagrams representing one or more embodiments of theinvention do not inherently indicate any particular order nor imply anylimitations in the invention.

Embodiments of the present invention are discussed herein with referenceto FIGS. 1 to 5. However, those skilled in the art will readilyappreciate that the detailed description given herein with respect tothese figures is for explanatory purposes as the invention extendsbeyond these limited embodiments.

Although the present invention has been described in terms of specificembodiments it is anticipated that alterations and modifications thereofwill no doubt become apparent to those skilled in the art. It istherefore intended that the following claims be interpreted as coveringall such alterations and modification as fall within the true spirit andscope of the invention.

In one embodiment of the present invention, the scan system usesadjacent and alternative channel conditions to find a vacant orunoccupied channel within a band and provides the vacant channel as thetransmitting channel. The adjacent channel is the channel which isimmediately above or below the designated channel while the alternativechannel is the channel which is at two channel spacing above or belowthe designated channel. Different decision metric is used to find thebest channel. Two fast signal level detectors are used, one to measurethe on-channel signal level and another to measure the signal level ofadjacent and alternative (or out-of-channel) channel signal levels.Scanning of channels within the band is done by initializing a search tocompare the on-channel signal level, V_(s), of a particular channel witha predetermined threshold, V_(ith). If it is determined that V_(s) islarger than or equal to V_(ith), the particular channel is rejected,however, if V_(s) is smaller than V_(ith), the on-channel signal levelto the out-of-channel signal level ratio, CIR, is compared with apre-determined threshold CIR_(th). If CIR is less than CIR_(th), thesignal level V_(s) is compared to find the channel with the lowestsignal level and the found channel is declared the best channel. Thesignal level of the best channel is recorded. In a following scan, thesignal level of the best channel is first read and compared with arecorded value and if there is no increase detected by a predeterminedvalue, V_(hys), the current best channel is used and nothing is updated,however, if the change is higher than V_(hys), the process returns andcontinues from the initial searching step.

It should be noted that RSSI is an example of a measurement of thequality of the signal and other types of measurements, such assignal-to-noise ratio (SNR), center frequency deviation or others knownto those skilled in the art or any combinations thereof is contemplated.In this respect, RSSI, as used herein, is an example of figure of merit(FOM) or quality measurement representing a measurement of the signalquality.

Dividing the bands into ‘n’ number of sub-bands advantageously allowsthe scan system to measure the RSSI value (or FOM) more accurately andin a shorter time period when compared with scanning the entirety of theFM band from beginning to end, as done by prior art techniques. This isso because the sub-bands can be scanned with a finer granularity than isgenerally done when an entire band is scanned.

Additionally, the scan system uses a digital signal processing(DSP)-based adaptive signal strength measurement which is advantageouslyfaster than the current conventional system used by existing scanningsystems. A DSP-based signal strength measurement system that is adaptiveallows for programmable-setting its coefficients, which advantageouslyprovides for faster tuning thereby improving system performance.

FIG. 1 shows a block diagram of the scan system 26, in accordance withan embodiment of the present invention. The scan system 26 is shown toinclude channel condition assessment (CCA) tuner 12, CCAanalog-to-digital converter (ADC) 14, filter 51, filter 52, on-channelFOM block 16, out-of-channel FOM block 18 and CCA finite state machine(FSM) 20. RX Antenna 5 and microcontroller unit (MCU) 22 are showncoupled to scan system 26. The MCU 22 is shown to include storage 24 andchannel frequency block 28. The RX Antenna 5 is shown coupled to the CCAtuner 12. The CCA Tuner 12 is shown coupled to the CCA ADC 14. The CCAADC 14 is shown coupled to both the filter 51 and the filter 52. Thefilter 51 is shown coupled to the on-channel FOM block 16. Theon-channel FOM block 16 is shown coupled to the CCA FSM 20. The filter52 is shown coupled to the out-of-channel FOM block 18. Theout-of-channel FOM block 18 is shown coupled to the CCA FSM 20. Whenusing the scan system 26 in an FM band application, the CCA tuner 12operates as an FM tuner. When using the scan system 26 in an AM bandapplication, the tuner 12 operates as an AM tuner.

In some embodiments, the MCU 22 is located within the radio transmittersystem or the radio receiver system. In other embodiments, the MCU 22 islocated externally to the radio transmitter system or the radio receiversystem. In some embodiments, the MCU 22 is part of the scan system 26and in other embodiments, the MCU 22 is located externally to the scansystem 26.

The filter 51 and the on-channel FOM block 16 collectively comprise theon-channel selection block 19. In some embodiments, the filter 51 andthe on-channel FOM block 16 are physically the same block and in otherembodiments, they appear as in FIG. 1 as separate structures. The filter52 and the out-of-channel FOM block 18 collectively comprise theout-of-channel selection block 21. In some embodiments, the filter 52and the out-of-channel FOM block 18 are physically the same block and inother embodiments, they appear as in FIG. 1 as separate structures.

RX Antenna 5 is shown to receive the signal, in the form of an analogsignal, and to transmit the same to the tuner 12. Tuner 12 receives theanalog signal is operative to select a single station by excludingsubstantially all others and to generate a tuned analog signal 30 foruse by the ADC 14. Tuner 12 is user-programmable to select a start andstop frequency range and a step frequency and in this manner divides theband into multiple sub-bands.

In an exemplary embodiment, the selected step frequency is 200 kHz andthe band is divided into sub-band. ADC 14 is operative to receive thesignal 30 and to convert the same to digital signal 32. The signal 32 isthen coupled onto filter 51 and filter 52. Filter 51 is designed toselect substantially only the on-channel frequencies and tosubstantially disregard the out-of-channel frequencies from the signal32 to generate the on-channel signal 34. Filter 52 is operative toselect substantially only the out-of-channel frequencies and tosubstantially disregard the on-channel frequencies from the signal 32 togenerate the out-of-channel signal 36.

The filter 51 is further operative to transfer the on-channel signals 34to the on-channel FOM block 16. The on-channel FOM block 16 is operativeto measure the FOM of the on-channel signals 34 (a measurementrepresenting the measurement of signal quality of the on-channelsignal), and the out-of-channel FOM block 18 is operative to measure theout-of-channel signals 36 (a measurement representing the measurement ofsignal quality of the out-of-channel signal). In one embodiment of thepresent invention, both blocks 16 and 18 use an adaptive time constantwhich advantageously allows for fast user-programming of settings (suchas coefficients) and fast FOM calculation.

A scan of the band performed at a low bandwidth yields more accurateresults, as more noise is removed, than a scan at a high bandwidth.However, scanning with the high bandwidth is less time-consuming tocomplete. The scan system 26 advantageously uses an adaptive timeconstant to yield accurate scans of the FM band in a short amount oftime. The adaptive time constant changes to produce a scan that is veryfast initially and then becomes increasingly slower. In an exemplaryembodiment, the scan is performed at least five times faster than thatrealized by prior art techniques. The on-channel FOM block 16 isoperative to generate an FOM on-channel signal 38 and the out-of-channelFOM block 18 is operative to generate an FOM out-of-channel signal 40,both of which are received by the CCA FSM 20.

The CCA FSM 20 is operative to ultimately select the best candidate openchannel. The MCU 22 records the FOM measurements from the on-channel FOMblock 16 and the out-of-channel FOM block 18 and calculates theon-channel to out-of-channel FOM ratio. More specifically, the signals38 and 40 are used to calculate the on-channel to out-of-channel FOMratio of these signals by dividing the signal 38 by the signal 40. TheMCU 22 is further operative to compare the on-channel to out-of-channelFOM ratio to a programmable (predetermined) threshold value. If thecalculated ratio is below the threshold, the channel is selected, and ifthe ratio is above the threshold, the channel is not selected.Alternatively, this comparison may be done by comparing the ratio tobeing above or equal to the threshold and/or less than or equal thereto.While the on-channel FOM may indicate an open channel or an un-occupiedchannel, i.e., low on-channel RSSI, a high out-of-channel RSSI indicatesthe existence a strong adjacent channel. This scenario may be indicatedby a low on-channel FOM to out-of-channel FOM ratio.

The CCA FSM 20 is operative to perform the initial sub-band scan. Thatis, it compares the FOM of each of the channels within a sub-band todetermine a candidate channel based on the channel with the lowest FOM.It is noted that alternatively, rather than performing the initialsub-band channel scan prior to the FOM that is performed for adjacentchannels of the candidate channels, the initial sub-band channel scanmay be done after the adjacent FOM channel determination.

It should be noted that practically, a hysteresis type of threshold ispreferred in that rather than a specific value determining thethreshold, the threshold is a range below which, the channel is selectedand above which the channel is not selected or vice versa. In oneembodiment of the present invention, MCU 22 is operative to compare theon-channel to out-of-channel FOM ratio to a hysteresis range ofthresholds having an upper range and a lower range, wherein the FOMratio being below the range indicates that the channel is to beselected, and the FOM ratio being above the range indicates that thechannel is not to be selected

The MCU 22 is operative to integrate the hardware-based system 26 withblock 28 and storage 24. Both block 28 and storage 24 are included inthe MCU 22, in an exemplary embodiment. It is understood however, thatthey may be executed elsewhere or each on a different platform. Block 28is operative to specify the start and stop frequency range and stepfrequency used by system 26 and optionally to maintain a history of“best” channel and update the same periodically. Storage 24 is operativeto store past open channel search results. Storage 24 is optional butwhen used improves tuning by allowing for a more accurate selection ofan open channel because periodic scans are performed and used to compareto a previous (or current) “best” channel and if an improvement is notedover the current best channel, the best channel is updated to be thethat which showed an improvement. In this manner, a history ismaintained and “best” channel is updated to track the currentsurroundings of the system 26. This is advantageous particularly whenthe system 26 is used in a portable device and the location of theportable device changes.

The scan system 26 can also be used in a radio receive system to helplocate a channel presumably having a good signal quality. The featurefor a radio receive to automatically tune to a channel with good signalquality is often called auto seek or auto search in the field. This is auseful and convenient and improves user experience with radio listening.Opposite to the radio transmitter applications where the goal is toidentify an un-occupied or vacant channel, the goal for the scan systemin the radio receiver applications is to identify a channel with goodsignal level which presumably delivers good quality. This conventionalapproach works satisfactorily to a certain degree. However, there arealways cases that the criterion solely based on received signal strengthfails to pick a good channel.

In real world environment, the signals received at a receive antennarepresent a summation of all radio signals from various sourcespropagated through their paths to the receive antenna. In an urbanenvironment where a receiver may be surrounded by many tall buildingsblocking a line-of-sight path between the receiver and a transmittingradio station and causing severe multi-path scenario where the signalarrives at the receive antenna from multiple routes. The multiple copiesof the signals may interfere with themselves and result in poor audioquality even though the received signal level may be high. In anotherscenario, a received signal level may be good enough to deliver a goodaudio quality if there were no strong signal in the adjacent channels. Acriterion solely based on the on-channel signal level may fail todistinguish when a good audio quality may be achieved.

The scan system 26 in the current invent can examine the on-channel FOMas well as the out-of-channel FOM and make a decision about the qualityof the channel. In one exemplary case, the scan system 26 may comparethe on-channel FOM with a threshold V_(R) and skip the channel if theon-channel FOM is below the threshold V_(R1). If the on-channel FOM isabove the threshold V_(R), the out-of-channel FOM will be checked. Ifthe out-of-channel FOM is above a threshold V_(R2), the channel isskipped. Otherwise the channel is selected as a valid channel.

While the above exemplary usage of the scan system 100 for a radioreceiver system compares the on-channel FOM and out-of-channel FOM withrespective thresholds as a method to determine whether the channel is avalid channel or not, it will be apparent, however, to one skilled inthe art, many other criteria may be applicable as well to achieve thesame or similar results.

FIG. 2 shows a block diagram of a radio transmitter system 200incorporating the scan system invention. The radio transmitter systemmainly comprising three components: transmit path circuits 250, the scansystem 26, and a master FSM 260. The transmit path circuits 250 receivesaudio signal from the audio input interface 210 and performs a chain ofprocessing to convert the audio signal into radio frequency signal fortransmission through the TX antenna 205. The chain of processing maycomply with an FM modulation standard such as the US FM broadcasting inthe 88 to 108 MHz band or an AM modulation standard. The audio inputinterface accepts a supplied audio signal either in an analog or adigital format. If the audio signal is in the analog format, the analogsignal will be coupled to audio ADC 211 through signal line 205. If theaudio signal is in the digital format, it will be coupled to the audiointerface 210 through signal line 206 without passing through the audioADC 211. The signal 212 from the audio interface 210 is then passed totransmit digital signal processing (DSP) block 215.

The transmit DSP plays a key role as to convert the audio input signalinto a modulated signal suited for transmission. In the example fortransmission complying with US FM broadcast in the 88 to 108 MHz band,the transmit DSP block 215 will perform audio pre-emphasis on the audiosignal and create FM multiplexed stereo audio. The FM multiplexed stereoaudio is then subject to FM modulation done digitally by the transmitDSP block 215 and the digitally modulated FM signal is then outputted todigital-to-analog (DAC) converter 220 through signal line 217. This FMmodulated signal in the analog format is ready for transmission at aselected FM channel.

The transmit tuner 225 receives the analog modulated signal from the DAC220 through signal line 222. The transmit tuner translates the analogmodulated signal to a channel in the FM band by mixing the analogmodulated signal with a mixing signal which is typically generated froma local oscillator (LO). A target transmitting frequency is usuallyachieved by mixing the analog modulated signal with an appropriate LOfrequency. In order to deliver high quality audio, the channel selectedpreferably is free from possible interferences from FM broadcaststations or other radiation sources. The scan system is incorporated inthe system for the purpose to determine a best channel for the system totransmit. An optional power amplifier 230 is shown in FIG. 2 if highpower transmission is desired. The power amplifier 230 receives themodulated signal up converted to the FM band from signal line 227 andoutput the amplified signal to TX antenna 205 through signal line 237.

The master FSM 260 provides all needed control and communication tovarious parts of the system. For example, the master FSM 260 may acceptthe channel selected by the CCA FSM 20 of the scan system 26 and uses itto select the transmitting frequency for the transmit tuner 225. The FSMis well known in the art and has been widely used for system controlthat does not require complex control. The FSM has known for itsadvantages of simplicity in implementation and quick in execution. Forthe intended use in the radio transmit system or the radio receivesystem where many system parameters such as the on-channel FOM and theout-of-channel FOM are computed by the digital signal processing, i.e.,the CCA block in the scan system, the FSM control is mainly for makingdeterministic decision based on the computed parameter. Therefore, therequired decision making by the FSM is relatively light. Therefore, theFSM approach as a system control matches with the intended systemnicely.

In FIG. 2, two separate antennas 5 and 205 are shown. For thecost-saving reason, a single antenna can be shared by the scan system 26and the transmit path circuits 250. When a shared antenna is used, thesystem will cease transmission when the scan system 26 is connected tothe shared antenna and receives signals. Since a new channel search isneeded before initial transmission or the system is experiencinginterference resulting in poor audio quality, ceasing transmissionmomentarily for the scan system to search for a new channel will notcause operational inconvenience.

In FIG. 2, an optional digital interface 270 is shown. The digitalinterface 270 serves to provide user interface to the master FSM 260.For example, a user may desire to increase the transmit power byadjusting the power amplifier 230. The user's input may be enteredthrough the digital interface 270 into the master FSM 260. The masterFSM 260 then controls the output power for the power amplifier 230.

FIG. 3 shows an alternative radio transmit system 300 incorporating thescan system 26 wherein parts of the scan system are implemented in thetransmit path circuits 350. As described previously, the scan systemuses a digital signal processing (DSP)-based adaptive signal strengthmeasurement. The DSP-based signal strength measurement corresponding tothe CCA block 60 can be performed or mostly performed by the transmitDSP block 215. Therefore it will be advantageous to reuse the availableresources in the transmit DSP block 215 and to augment it with othercomponents required to perform the function of CCA block 60. Theaugmented transmit DSP block that is capable of performing the functionof the CCA block 60 is shown in FIG. 3 as the transmit DSP block 315.

On the other hand, the CCA FSM 20 may be merged into the master FSM 260though few resources can be shared between the CCA FSM 20 and the masterFSM 260. Merging the CCA FSM 20 and the master FSM 260 will make thesystem partition conceptually simpler and may also slightly reduce theoverall gate count if the system is implemented in integrated IC. Thecombined FSM is shown in FIG. 3 as master FSM 360.

Again, the TX antenna 205 and the RX antenna 5 may share the sameantenna as described previously.

FIG. 4 shows a radio receiver system 400 incorporating the scan system26. The radio receiver system 400 comprises primarily three majorcomponents: receive path circuits 450, the scam system 26 and master FSM460. The receive path circuits 450 are coupled to RX antenna 405 toreceive signals in a band through the signal line 407. The receive tuner410 will be tuned to a channel of the received signal wherein thefrequency of the tuned channel can be controlled. The analog-to-digitalconverter (ADC) 415 converts the received signal 412 into a digitalsignal 417. The receive DSP block is responsive for a chain of digitalsignal processing. For an FM broadcast receiver, the receive DSP blockwill perform channel filtering, digital demodulation on the digitizedreceived signal 417, FM stereo de-multiplexing of the demodulated signalinto a pair of digital audio, and de-emphasis of the pair of digitalaudio. The generated digital audio signal 422 can be outputted throughthe audio output interface 425 as the digital audio output signal 456 orpassed through the audio digital-to-analog converter (DAC) 426 toprovide an analog audio output 455. The channel filtering for a selectedchannel is well known in the art and its main purpose is to selectivelypass the desired signal while blocking un-wanted signal. Filters for thechannel filtering are usually characterized by the bandwidth, pass-bandripples, stop band ripples, roll-off factor, and etc. A set of filtersor filters with a set of programmable parameters with desiredcharacteristics may be used and the one best matched with the underlyingchannel condition may be selected. In order to simplify filter design tofulfill the required channel filtering, often a model filter havingprogrammable parameters or coefficients is used, such as Butterworthbandpass filter, is used.

The scan system 26 will be responsible to select a valid channel for thereceive path circuits to tune to. The CCA FSM 20 will be configured tooutput a channel which has a high on-channel FOM and a lowout-of-channel FOM. This is an indication that the channel may have goodquality and is free from potential interference from neighboringchannels. For the radio receiver to receive this channel and produce abest audio quality, a full bandwidth filter to pass the channel can beused without concerning possible interference from neighboring channels.However, there are cases that a channel may show a high on-channel FOMand a high out-of-channel FOM as well. This is an indication that whilethe selected channel may be valid, it is subject to potentialinterference from neighboring channels, To minimize the possibleinterference without noticeably degrading the quality of the selectedchannel, a channel filter matched to the on-channel and out-of-channelconditions has to be used, Therefore, a set of channel filters may beused to control the channel filtering and the selection of the filtersis related to the out-of-channel FOM. As will be understood by a skilledperson in the art, many other criteria may be used by the CCA FSM toselect a channel and to control the channel filtering that will resultin good audio quality.

The master FSM 460 is responsible for control and communication withvarious parts of the system. For example, the master FSM 460 will acceptthe channel selected by the CCA FSM 20 and cause the receive tuner 410to tune to the selected channel.

FIG. 4 also shows an optional digital interface 270 allowing a user'sinput to be entered through the digital interface 270 into the masterFSM 460.

FIG. 5 shows a radio receiver system 500 incorporating the scan system26 wherein the scan system is implemented in the receive path circuits550 and the master FSM 560. The receive tuner 510 can be configured tobe used as a radio receiver tuner or a CCA tuner depending on whetherthe system is under radio receiving mode or auto seek mode. The outputsignal 512 can be either a tuner radio channel or a tuned CCA signal.Since the ADC 415 and CCA ADC 14 in FIG. 4 have similar characteristicsand they can share the same ADC 515 as shown in FIG. 5. The receive DSPblock 520 receives the digitized signal 517 and can be configured as aradio receiver DSP or a CCA DSP. When the receive DSP block 520 isconfigured as a radio receiver DSP, it will output digital audio signal422. When the receive DSP block 520 is configured as a CCA DSP, it willprovide the on-channel FOM and the out-of-channel FOM to the master FSM560 to select a valid channel.

The transmit DSP block and receive DSP block are referring to devices ormeans that are capable of performing required signal processingdigitally. The transmit DSP block and receive DSP block may be a devicesuch as a programmable digital signal processor, a CPU, amicrocontroller, digital logics, or other forms of device capable ofperforming signal processing digitally. The DSP means may be implementedas instruction codes stored in computer readable storage media,generally known as software or firmware. Also the transmit DSP block andreceive DSP block may be a mixed of device and means. For example, aparticular type of operation, such as multiplication, may be implementedby a dedicated device while other operations such as decision making anddata movement may be implemented in software or firmware executed on amicrocontroller.

Thus, in accordance with the various embodiments of the presentinvention, a radio transmit system and a radio receive systemincorporating the scan system are disclosed. The systems are partitionedinto various component blocks to fulfill the required processing.However, it is understood by a skilled person in the art that there aremany different ways to partition a radio transmit system or a radioreceive system to achieve the same goal.

As known by one of ordinary skill in the art, this invention, includingany logic circuit (block) or transistor circuit, may be modeled,generated, or both by computer based on a description of the hardwareexpressed in the syntax and the semantics of a hardware descriptionlanguage (HDL). Such HDL descriptions are often stored on acomputer-readable medium. Applicable HDLs include those at the layout,circuit netlist, register transfer, and/or schematic capture levels.Examples of HDLs include, but are not limited to: GDS II and OASIS(layout level); various SPICE languages, and IBIS (circuit netlistlevel); Verilog and VHDL (register transfer level); and Virtuoso customdesign language and Design Architecture-IC custom design language(schematic capture level). HDL descriptions may also be used for avariety of purposes, including but not limited to layout, behavior,logic and circuit design verification, modeling, and/or simulation.

What is claimed is:
 1. An integrated radio receiver comprising: areceive antenna interface; an audio output interface; receive pathcircuits coupled to the receive antenna interface and audio outputinterface, wherein the receive path circuits include a receive tunerhaving a tunable receiving frequency and a receivedigital-signal-processing block having controllable channel filtering; ascan system operative to receive signals within a band from the receiveantenna interface and to generate a valid channel and a channelfiltering control parameter; and a master finite state machine (FSM)coupled to the receive path circuits and the scan system to providecontrol and communication, wherein the valid channel generated by thescan system is applied to select a receiving frequency for the receivepath circuits and the channel filtering control parameter is applied tocontrol the channel filtering, and wherein the scan system comprises: achannel condition assessment (CCA) tuner coupled to the receive antennainterface and operative to tune within the band and operative togenerate a tuned analog signal; a CCA analog-to-digital converter (ADC)coupled to the CCA tuner and operative to convert the tuned analogsignal to a digital signal; an on-channel selection block responsive tothe digital signal and operative to generate a on-channel signal byselecting only on-channel frequencies and substantially disregardingout-of-channel frequencies from the digital signal and operative togenerate an on-channel figure of merit (FOM) representing a signalquality measurement of the on-channel signal; and an out-of-channelselection block responsive to the digital signal and operative togenerate an out-of-channel signal by selecting only the out-of-channelfrequencies and substantially disregarding the on-channel frequenciesfrom the digital signal and operative to generate an out-of-channel FOMrepresenting the signal quality measurement of the out-of-channelsignal.
 2. The integrated radio receiver of claim 1, wherein the scansystem further including a CCA finite state machine (FSM) responsive tothe on-channel FOM and the out-of-channel FOM and operative to selectthe valid channel based on the on-channel FOM and to select the channelfiltering control parameter based on the out-of-channel FOM.
 3. Theintegrated radio receiver of claim 1, wherein integrated radio receiverincludes a digital interface coupled to the master FSM for providing auser interface to the master FSM.
 4. The integrated radio receiver ofclaim 1, wherein the scan system uses an adaptive scan time.
 5. Anintegrated radio receiver comprising: a receive antenna interface; anaudio output interface; receive path circuits coupled to the receiveantenna interface and audio output interface, wherein the receive pathcircuits include a receive digital signal processing (DSP) block havingcontrollable channel filtering, an analog-to-digital converter (ADC) anda receive tuner having a tunable receiving frequency; a scan systemoperative to receive signals within a band from the receive antennainterface and to generate a valid channel and a channel filteringcontrol parameter, the scan system comprising: (a) means responsive tothe received signal in the band to tune and operative to generate atuned analog signal; (b) means for converting the tuned analog signal toa digital signal; (c) means responsive to the digital signal forgenerating an on-channel signal by selecting on-channel frequenciesthereof and substantially disregarding out-of-channel frequenciesthereof and for generating an on-channel figure of merit (FOM)representing a signal quality measurement of the on-channel signal; (d)means responsive to the digital signal for generating an out-of-channelsignal by selecting the out-of-channel frequencies thereof andsubstantially disregarding the on-channel frequencies thereof and forgenerating an out-of-channel FOM representing the signal qualitymeasurement of the out-of-channel signal; (e) means for selecting a bestchannel within the band based on the on-channel FOM as the validchannel; and (f) means for selecting the channel filtering controlparameter based on the out-of-channel FOM; and a master finite statemachine (FSM) coupled to the receive path circuits and the scan systemto provide control and communication, wherein the valid channelgenerated by the scan system is applied to select the receivingfrequency for the receive path circuits and the channel filteringcontrol parameter is applied to control the channel filtering.
 6. Theintegrated radio receiver of claim 5, wherein the means responsive tothe received signal in the band to tune and operative to generate thetuned analog signal is implemented in the receive tuner.
 7. Theintegrated radio receiver of claim 5, wherein the means for convertingthe tuned analog signal to a digital signal is implemented in the ADC.8. The integrated radio receiver of claim 5, wherein the means for theon-channel FOM and the means for out-of-channel FOM are implemented inthe receive DSP.
 9. The integrated radio receiver of claim 5, whereinthe means for selecting the best channel as the valid channel isimplemented in the master FSM.
 10. The integrated radio receiver ofclaim 5, wherein the receive path circuits further comprises an audiodigital-to-analog converter (DAC) to accommodate an analog audio outputsignal.
 11. The integrated radio receiver of claim 5, wherein integratedradio receiver includes a digital interface coupled to the master FSMfor providing a user interface to the master FSM.
 12. The integratedradio receiver of claim 5, wherein the scan system uses an adaptive scantime.